Abstract: A book bag having a primary compartment and a plurality of substantially identical secondary compartments which are designed to function independently of each other while in a unitary arraignment. The compartments can be converted to a fully open relationship which allows for easy storage into narrow upright lockers. Each compartment has inner and outer parallel side panels connected by a bottom, top, and two ends. The compartments are interconnected in a side by side relationship to the side panel of a mating compartment by zipper elements. Secured to the inner panel of each compartment is a shoulder harness to allow the book bag to be carried in typical fashion on one's back. Individual compartments may also be carried by a handle secured to the top. Centrally positioned on the outer side panel is an expandable envelope designed for easy retrial of homework assignments or the like. Pockets are also provided on the ends of a compartment for storage of pens, rulers, pencils or other school supplies.